表遗传学调控及相关信号转导途径在铝所致L－LTP维持损害中的作用与机制研究

Aluminum (Al) can impact cognitive function. However, the mechanism underlying these adverse effects is not clear. Late phase long—term potentiation(L—LTP) is closely related to long—term memory(LTM).Our previous work has revealed that Al impairs LTM via the impairment of L—LTP maintenance in CA1 area of hippocampus, which is the electrophysiological basis. And then, we further elucidate the key mechanism for L—LTP maintaining damage is the interference of Al by inhibiting cAMP—cPKA—pCREB signaling. CREB is a molecular switch of LTM formation. The memory damage caused by Al may be related to inhibiting the expression of CREB target genes. Gene expression is affected by many factors, epigenetic patterns play an important role in the regulation of gene expression and memory formation. The activation degree of MAPK/ERKs signaling pathways affects not only the activation status of CREB, but also the level of epigenetic regulation. Al may damage LTM with the interference to the pattern of epigenetic regulation, CREB activation, and then restraining the normal transcription of CREB target genes by inhibiting MAPK/ERKs signaling pathway, especially MSK1/2 and RSK. The purpose of this study is to validate the hypothesis mentioned above from the aspect of epigenetic regulation mode, active state of related signaling pathway by experiments in vivo and in vitro. The results of this study will provide scientific basis for searching the molecular target points of effective intervention.

铝影响认知功能，但机制尚未阐明。L—LTP与长时记忆密切相关。我们前期工作提示，铝损害大鼠长时空间记忆，首次提出海马CA1区L—LTP维持受损是其电生理基础，而后进一步阐明铝干扰cAMP—cPKA—pCREB信号通路是其损害L—LTP维持的关键机制。CREB是长时记忆形成的分子开关。铝对记忆的损害可能与抑制CREB靶基因表达有关。基因表达受多种因素影响，表遗传学模式在调控基因表达和记忆形成中发挥重要作用。MAPK/ERKs信号通路激活程度不仅影响CREB活化状态，而且与表遗传学调控水平密切相关。铝可能通过抑制MAPK/ERKs信号通路尤其阻碍MSK1/2和RSK功能，干扰表遗传学调控模式和CREB活化，抑制CREB靶基因转录而损害长时记忆。本研究拟采用整体动物与离体脑片结合的方法，从表遗传学调控模式、相关信号通路活化程度等不同层面和角度验证上述假设，为寻找有效干预的分子靶点提供依据。

铝具有明显的神经毒性，铝暴露所导致的人体健康损害尤其神经系统疾患已成为令人关注的全球性公共卫生问题。.本课题以Wistar子代大鼠为实验对象，以AlCl3为受试物，连续染毒3个月。课题采用多种实验手段，包括神经行为学、神经电生理学、组织病理学、生物化学和分子生物学等技术手段，通过观察动物学习记忆能力指标（逃避潜伏期、错误次数等）变化、电生理指标（PS、EPSPs）改变、细胞内表遗传学指标（乙酰化组蛋白H3、HATs）变化、记忆相关基因（ap-1、gdnf等）表达变化和记忆相关蛋白（AP-1、GDNF等）含量变化，结合神经细胞超微结构异常等开展了一系列的研究。.结果表明动物在Morris水迷宫检测中认知功能损害。在透射电镜下，海马、皮质和纹状体的神经元、突触的超微结构损害随染毒剂量增加而加重。铝暴露导致子代大鼠海马组蛋白H3乙酰化水平降低，伴随HAT1蛋白表达和活性降低。铝暴露导致子代大鼠海马组蛋白H3K9me2水平升高，伴随G9a蛋白表达和活性升高，PHF8蛋白表达和活性降低。.因此，我们证实了研究假设：铝通过干扰表遗传学调控模式和CREB磷酸化，从而影响CREB靶基因的正常转录而损害长时记忆。研究结果明确了表遗传学修饰在铝所致神经系统损伤中的有害作用。.项目圆满完成各项指标检测，主持人超额完成既定任务，成果显著。发表北大中文核心期刊论文12篇（另外，投出或待刊的中、英文文章9篇，将产出21篇论文）。培养硕士研究生5名。依托该项目获得科研奖励7项。获得中青年学术带头人国家级人才培养计划资助1人次。参加国内、国际学术会议共5人次等。.应用方向集中在儿童智力发育及认知损害干预、成年期铝相关疾病防治等。本成果推广关乎国家少年儿童健康成长和智力发育，关乎祖国同胞身体素质，关乎国家居民身体健康和全面小康。.